1. Field of the Invention
The present invention relates to solder fillers for aluminum body parts and methods of applying solder fillers to aluminum body parts.
2. Background Art
Body fillers have been widely used in the automotive industry to provide smooth and continuous surfaces by covering and concealing surface imperfections such as spot welded joints or body surface flaws. Numerous compositions have been used as body fillers for steel automotive body panels. For example, lead-containing body fillers had been heavily utilized. Environmental concerns have caused the automotive industry to move away from lead-containing fillers and focus on developing lead-free compositions.
Polymeric materials have been used as fillers. However, such materials bond mechanically to the body part surface rather than metallurgically. The mechanical bonds are much weaker than metallurgical bonds. In addition, metallic components often must be added to the polymeric materials in order to make the polymer conductive for electro-deposition coating. Additionally, the polymeric material softening temperature is typically very close to the paint baking oven temperature. As a result, during the paint drying stage, the polymeric material can melt, thus destroying the paint finish.
Body fillers have been proposed for aluminum automotive body panels, as well. Some body solders fillers, thermally-sprayed solder fillers, and MIG-welded fillers used on steel panels have been unsuccessfully applied to aluminum body parts. Many thermal sprayed and MIG welded filler compositions for steel body parts have the potential to produce stress cracks and heat distortion when used with aluminum body panels. This detrimental result occurs because the processing temperature required for the steel solder filler is too high relative to the melting point temperatures of the aluminum alloys used in aluminum body panels.
Aluminum/silicon alloys have also been applied to aluminum pillar joints using MIG welding and thermal spraying techniques. However, these application processes have the potential to produce stress cracks and heat distortion when used with aluminum body panels since the processing temperature for the aluminum/silicon alloys is relatively close to the melting point temperatures typical of aluminum body panel alloys.
It would be desirable to provide solder fillers and methods of applying the solder fillers to aluminum body parts that provide favorable thermal and mechanical properties. It would also be desirable to provide new solder fillers for aluminum body parts and application methods that provide favorable thermal and mechanical properties, including the inhibition of stress cracking and heat distortion of the aluminum body parts. These and other advantages will become more apparent to those of ordinary skill in the art upon reference to the following description.